1. Field of the Invention
The present invention relates to a device for making of porous concrete intended for casting purposes, e.g., for casting portions of buildings such as foundation plates, walls and beams wherein principally cement, water and a frothing agent are simultaneously mixed in a way that air pores are produced in the mixture.
2. The Prior Art
A known method for making porous concrete involves mixing cement, sand, and water in a concrete mixer, after which a separately produced froth is lead into and mixed in the concrete. The concrete mixer constituted by a stationary tank having a rotating mixing screw or similar element therein. The froth is produced by a device in which a frothing agent is mixed with air and eventually water so that a froth with small air bubbles is obtained. A device for producing such a froth is described in the Swedish Patent Publication No. 156215.
In order to obtain a uniform quality of the cast porous concrete, i.e., such that it has a uniform density and strength, it is required that the included raw material be mixed in the right proportions. With continuous production, this has been found to be difficult as careful measurement of the flows of raw material and a watching of the mixing times. Further, an effective mixing of the air is required in order not to overly extend the mixing time.